Restoring Archived Documents-Please Help


I was installing a new program onto my Mac recently, and I accidently reinstalled the Macintosh program instead. I found my archived documents but I can't access them. Why can't I access them? How can I access them?
Please help me! T_T
This is my school computer, and I need these documents for my classes right away.
First of all, what kind of Mac is it? Second, the OS X (if it is OS X and please list the version of OS X) was not re-installed unless you were using an install disk. If you do have OS X, go to Application-> Utilities->Disk Utility and "Repair Permissions" with Disk Utility.
sorry, its a Powerbook G4
OS X .. tiger if i remember correctly and it was most definately reinstalled x.x because the program told me to use that disk and i hit the wrong button during the installation.
Thank you though. ^.^